This invention relates to bearings for supporting rotary members and more particular to ball bearings.
As is well known in this technology, there are sundry ball bearings for supporting rotating shafts and the like and are characteristic of typically transmitting loads and supporting axial or thrusts loads and often employed for carrying heavy radial loads. Typically, the balls of a ball bearing configuration is supported between a pair of concentric rings, an inner race and an outer race and the balls lie in a plane normal to the axis of rotation. Also, particularly in high speed operation, the races are pre-loaded so as to keep the balls in radial alignment. Obviously, as is well known to those skilled in the art, in these types of bearings, whether it be the single or double row ball bearings configuration, a misalignment of the balls relative to each other would cause the misaligned ball to rotate faster than the other balls, creating heat and friction, resulting in failure or premature wear of the bearing.
I have found that I can obtain an improved ball bearing by judiciously orienting the balls in the bearings so that the circumferential path of the balls is somewhat in the shape of a helical path. In this arrangement each of the balls follow an independent path alleviating the wear that would otherwise occur in the heretofore known ball bearing. The balls are supported in a cage and can be assembled with or without the inner race and/or outer race and do not require pre-loading. When assembled without the races, the ball for a given envelope is larger which is another feature that serves to enhance the wear characteristics of the bearing.
In many medical instrument applications, the ball bearings typically are utilized for radial loads inasmuch as the supporting mechanism typically requires the assembly and disassembly of the shaft or the like that is supported by the bearings. For example, in drills utilized in surgical operations the cutters are driven by a motor and the cutters are typically changed for different sizes and types. The Anspach Company, the assignee of this patent application, for instance, manufactures and sells the EMax(trademark) drill that is utilized with different sized and shaped cutters which cutters are slidably mounted into the drill.
Another example of the bearings utilized for surgical instruments is disclosed and claimed in U.S. patent application Ser. No. 09/962,989 filed on Sep. 25, 2001 entitled xe2x80x9cBearings For Surgical Instrumentsxe2x80x9d and assigned to the same assignee as this patent application, which is incorporated herein by reference. This patent application is being cited here because in one embodiment, this invention replaces one of the bearings in the Micro Dissection Attachment (MDA) disclosed in this patent application. As taught in the aforementioned patent application, the MDA utilizes journal bearings made from a polymer of polyimide resin and graphite composition and is judiciously configured so that there are two points of contact of the mating surfaces. This bearing configuration allows for the miniaturizing of the MDA at the distal end so as to enhance the line of vision of the cutter for the surgeon to facilitate the procedure in surgery. The journal bearing of this teachings also enhances the wear characteristics of the MDA. Like the journal bearing as taught in the U.S. patent application Ser. No. 09/962,989, supra, the ball bearing of this invention can be made sufficiently small so that it affords the characteristics of having a line of sight for the surgeon doing a surgical procedure similar to the characteristics that is sought after in the MDA application, while enhancing the load characteristics of the instrument. Additionally, while the present ball bearing of this invention affords a significantly miniaturized bearing wherein the diameter of the balls are in the order of 0.032 inch, for example, there is no limitation in the upper end of ball size of the bearing. Hence, for surgical instruments where the ball bearings only support radial loads, it is fundamentally important that the bearings sizes are small and factually, the smaller the bearing the better.
The bearing made in accordance with this invention affords the following characteristics although other characteristics may be realized:
1) The ball bearings when utilized without the races are larger in diameter and hence, enhance the wear characteristics of the bearing;
2) The balls do not roll on common tracts and hence, each ball runs on an independent track which enhances the wear characteristics of the bearing,
3) The bearing can be miniaturized so as to maintain a small diameter of the envelope;
4) the bearings are characterized as easy to manufacture, less expensive than heretofore known bearings, are maintenance free and are reliable and have a long operational life;
5) the material of the bearings can be any well known material, be it ceramic or metal;
6) pre-loading is not necessary;
7) the assembly and disassembly of the bearing are simplified in comparison to heretofore known ball bearings; and
8) misalignment of the balls is obviated.
An object of this invention is to provide an improved ball bearing.
A feature of this invention is that the balls are discretely off-set so that each ball lies in a different plane transverse to the rotating axis. There are no limits on the number or rows of balls that can be included in a single bearing and the number of rows and balls in each row are predicated on the particular design.
Another feature of this invention in certain embodiments, no races are utilized. In other embodiments the ball bearing can be constructed with or without the inner race and/or the outer race.
This invention is characteristic of enhancing the life of the bearing, adaptable for high speed operation, miniaturization for reducing the envelope size of the bearing chamber, low maintenance costs, and easy to assemble and disassemble.
The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings.